PROJECT SUMMARY Youth mild traumatic brain injury (mTBI, concussion) is a public health problem in the United States. Youth are felt to be particularly at risk for adverse outcomes from additive injury during recovery from mTBI. Thus, a critical aspect of care is determining when a child has recovered from mTBI such that a child can be medically cleared to return to sports and other high risk recreational activities without increased risk for adverse short- or long-term outcomes. While mTBI is defined as a physiological brain injury, current clinical measures for determining medical clearance to return to play after mTBI are not directly tried to brain physiology. The overall goal of this project is to evaluate markers of brain physiology in youth medically cleared to return to play after mTBI and how these markers relate to adverse events over the year following medical clearance. Specifically, we will investigate whether youth who have been medically cleared from mTBI by experts using the current gold-standard of clinical assessments show more subtle motor signs and/or anomalous functional brain connectivity compared to peers who have never had a mTBI and how long these findings persist. We will also evaluate whether motor and imaging findings predict rate of re-injury (musculoskeletal or mTBI) or clinically significant changes in emotional or cognitive functioning or health-related quality of life over the year following medical clearance. The aims of this project are to 1) evaluate whether youth medically cleared after mTBI show more subtle motor signs on a clinically-feasible measure at medical clearance and 3 and 12 months later, 2) evaluate for between-group differences in functional connectivity of resting state (default mode and dorsal attention) networks with premotor and motor brain regions at medical clearance and 3 and 12 months later, 3) determine if subtle motor signs are associated with functional brain connectivity in youth medically cleared after mTBI, and 4) evaluate the relationship between motor and imaging findings and occurrence of adverse events over the year following medical clearance. We will evaluate 70 youth aged 10-17 within 3 weeks of being medically cleared as recovered from mTBI and will re-evaluate the same youth 3 and 12 months later. We will similarly evaluate 70 age- and sex-matched youth who have never had a mTBI at three time points, baseline and 3 and 12 months later. At each time point we will compare groups with respect to motor subtle signs and functional connectivity of the dorsal attention network and default mode network with premotor and primary motor regions in the brain, both at rest and during a motor task. We will evaluate whether anomalous functional connectivity patterns in the mTBI group are associated with the presence of subtle motor signs. Lastly, we evaluate the relationship between motor and imaging findings and occurrence of re-injury or clinically significant change in functioning over the year following medical clearance. This project will help determine the adequacy of current clinical measures for evaluating medical clearance after youth mTBI and will set the stage for devising and evaluating strategies to reduce short- and long-term risks related to youth mTBI.